...and Missed on Purpose
The Problem:
But I spellchecked my document all the way through! How can you tell me it still has mistakes? Vile pedant!
The Solution:
You need to tweak the settings for the spelling checker. Choose Tools 
Options and click the Spelling & Grammar tab. See whether the "Ignore words in UPPERCASE" box is checked. If you use uppercase much in your documents (for example, for headings), uncheck this box to make sure that the spelling checker checks the uppercase words as well.
The "Ignore words with numbers" option (which is also checked by default) can also leave typos in your documen5tsI mean, documentsif you strike the number keys by mistak-e.
Tip: If the spelling checker still fails to catch obvious mistakes, check the language formatting of the mistakes. If someone has applied the "Do not check spelling or grammar" option to the text, the spelling checker will glide right past it. Select the text, choose Tools
Language Set Language, make sure the correct language is applied, and verify that the "Do not check spelling or grammar" box is unchecked.